Field of the Invention
The present invention refers to the field of the systems for managing vehicle compressors, which generally equip vehicles having a pneumatic braking system and/or pneumatic suspensions.
State of the Art
The vehicle compressor is generally controlled by a pressure sensor which measures the pressure of the compressed air within suitable accumulation tanks.
The calibration of the cut-off value, namely the pressure value measured in the tanks that determines the compressor stopping, is crucial in relation to the dimensions of the tanks, in order to cope with all the needs of the case, namely, for example, the need of lifting the suspensions, of activating an additional axle or of performing numerous braking repetitions.
A high number of pneumatic activations and an intense use of the pneumatic system may bring to determine a very high cut-off threshold.
Thus, in general, the cut-off value is identified at the planning stage.
Problems connected to the overheating of the compressor head when the vehicle engine runs at a high speed are known in the art.
The compressor, indeed, is mechanically connected to the internal combustion engine and takes from the latter the energy that is necessary to compress the air.
The energy absorption by the compressor is proportional to the number of revolutions per minute at which it is driven in rotation. This means that the activation of the compressor when the vehicle travels at a high speed, namely with a high engine speed, determines the maximum possible energy absorption by the compressor which tends to recharge the tanks in a very short time. This results in an overheating of the compressor head and in an overall worsening of the system engine/compressor, since the engine is asked to face by itself a high air resistance and since there is also a reduction of the volumetric efficiency of the compressor.
When the head of the compressor becomes particularly hot, the lubricating oil, which is generally in common with the internal combustion engine, tends to burn, worsening the performance of the compressor itself and of the post-treatment system of the compressed air. Moreover, the oil itself may leak, due to the high temperatures, and contaminate the post-treatment system of the compressed air and the whole compressed air circuit.
Furthermore, at the planning stage, it is necessary to appropriately dimension the pipes of the compressed air, in order to cool the air that passes through the post-treatment system. This means that suitable heat exchange elements and particularly long pipes for compressed air have to be provided, in order to take into account the temperature of the air sent by the compressor, also at the highest speed of rotation.
Furthermore, the stress of the elements forming the compressor is influenced by the back pressure in output from the compressor itself, thus with a high speed of rotation, such stress increases, increasing the wear of the compressor increases.